The present invention relates to looms in general, and more particularly to improvements in power looms of the type wherein the shuttles are caused to advance along an endless path.
Commonly owned British Pat. No. 1,158,031 discloses a loom wherein so-called gripper shuttles are caused to advance along an endless path which is defined by a track including the reed. The shuttle which is about to enter the open shed is accelerated by an endless toothed belt conveyor during travel along a relatively small portion of the arcuate section of the track preceding the reed. The conveyor is driven at an elevated speed which is deemed to be best suited for propulsion of the shuttle into the shed. The shuttle which has been accelerated to requisite speed is caused to engage the leader of the weft thread just before it enters the open shed. The weft thread is separated from the shuttle at the exit end of the shed, and the shuttle then returns into the range of the accelerating conveyor.
An advantage of a loom which employs gripper shuttles over the looms wherein the shuttles are caused to reciprocate back and forth in the region of the reed is that the gripper shuttles generate less noise. On the other hand, the speed of reciprocable shuttles at least matches the speed of gripper shuttles which are used in presently known looms wherein the gripper shuttles are caused to advance along an endless path. Moreover, the number of picks per unit of time in a loom with reciprocating shuttles is higher because a reciprocating shuttle can immediately reenter the shed as soon as it completes the advancement of weft thread in a first direction. In other words, a loom which uses reciprocable shuttles can save the time which is necessary to return a shuttle from the exit end of the shed, along the major portion of the endless path, and back into the range of the accelerating conveyor. Another drawback of presently known looms wherein the shuttles are caused to advance along an endless path is that, when the width of the woven fabric is quite pronounced and the warp threads are relatively thick, the shuttle which travels through the open shed is subjected to pronounced deceleration so that, when the width of the fabric exceeds a predetermined value and the diameter of the warp threads also exceeds a certain value, the weaving operation must be carried out in a loom which employs reciprocating shuttles. On the other hand, a loom which utilizes relatively lightweight gripper shuttles exhibits the important advantage that a lightweight shuttle constitutes a lesser danger to the attendants if it happens to be expelled from its endless path during travel through the open shed. At the same time, a presently known gripper shuttle which is caused to advance along an endless path is more likely to leave its path because the length of such shuttles is considerably less than the length of a reciprocating shuttle which carries its own supply of weft thread.